Native Tallgrass Prairie: Plant Community Development and Fine-Scale Structure Differ from Restored Prairies

Tallgrass prairie once extended from Manitoba south to Texas and southeast to Indiana covering 100 million hectares prior to European settlement. Today less than 0.1% remains in Illinois, Indiana, Iowa, and Wisconsin. Tallgrass prairie is a diverse ecosystem with small remnants (1–2 ha) containing a large number of plant species (> 100). With most of the ecosystem lost, active efforts to replant tallgrass prairie began in the 1930s. Unfortunately, even the oldest restorations do not have plant communities similar to native prairies. My research attempts to understand the factors limiting successful restoration of native plant diversity by focusing on intensive surveys of three native and two restored prairies in Iowa. In each prairie, I sampled seven 0.5 m2 plots using a frame with 49 grid points 10 cm apart and resurveyed these plots across successive years. I also collected soil cores and biomass and litter measurements in each plot. I analyzed plant community composition with a nonmetric multidimensional scaling ordination and fine-scale community structure with point richness and similarity metrics. Native prairies differed from restorations in plant community composition and had higher total carbon, nitrogen, and phosphorous, while restorations had higher plant available phosphorous. Native prairies also had higher richness from plot to point scales and lower similarity of neighboring plants at distances of centimeters. Restorations differ from native prairies at coarse and fine scales, and there was no indication that these restorations became more similar to native prairies over time. My work is the first to document fine-scale structure of plant diversity in native and restored prairies. By identifying that contemporary restoration practices do not result in plant communities that develop toward native prairies in composition, my work highlights our current limited understanding of the elements structuring plant communities and our ability to recreate this structure